Walk your cornfield now and if it's at the 6 to 8 leaf stage, you may see some speckling on the bottom leaf or two. Look more closely and some of it will likely wash away. It's dirt splashed onto the leaves during rain events over the past two weeks.
However, some of it may not wash away. If you look more closely it may look like disease lesions, albeit very tiny ones.
Is this the signal to apply fungicides? Probably not, most agronomists say. Danny Greene, Greene Crop Consulting, Franklin, examined a picture of a leaf from a field showing the speckling. His best guess is that it could be early season anthracnose leaf blight. This leaf came from a field that is conventionally tilled following soybeans.
What about yield? That's the big question. Green says that the severity of anthracnose leaf blight toward yield is very low. However, it can add stress to the plant, which can combine with other stresses to negatively affect production.
He reviewed a bulletin published by Iowa State University. The bulletin read: "resistant hybrids are commercially available, however resistance to the leaf blight phase is not highly correlated to resistance to the stalk rot phase."
Two hybrids were planted in the field, half on one side of the planter and half on the other. There did not appear to be a difference in whether one hybrid or the other was showing some leaf speckling.
The bottom line is that Greene says he wouldn't worry about a situation where only one leaf primarily has the early symptoms in the leaf he saw. Next time around, however, if you happen to be planting in no-till or continuous corn residue, you might ask your seedsman for a hybrid that includes resistance to anthracnose.
The small specks and lesions were not confirmed as anthracnose early season leaf blight by any other source.